Methods of the optical type or of mechanical type are known for measuring radius of curvature while making contact. Given the contact they make, they have the drawback of leading to damage, essentially to scratches on the article.
It is also known to measure the radius of curvature of an article without making contact, e.g. by interferometry. Such a method is complex to implement since it requires both very precise relative positioning between the article, and the work to be carried out in monochromatic light. Furthermore, with that method, a measurement step is relatively lengthy.